Changing a habit is hard work and different processes work for different people. When you're trying to change a habit, blogger Sam Spurlin recommends you slow the process way down and concentrate on the reasons why for a full month before you start.

Spurlin's idea is that you break down a habit into tiny chunks, and then concentrate on those chunks for an extended period of time. This doesn't just include your actions, but your thoughts. That means spending a month just thinking about the habit before making the change. For an example, Spurlin lays out one potential way to tackle the habit of biting your nails:

Spend a month thinking about and writing about why you want to stop biting your fingernails. Get every single reason, thought, and impulse down on paper.

Write down what you were doing and/or thinking about immediately before each time you started to bite your fingernails.

Keep a running tally of every time you notice yourself biting your fingernails.

Pick a hand. Focus on only using the nail clipper on that one hand for an entire month. Notice the difference between your hands. Which one feels better?

Switch hands. Focus on only using the nail clipper on that one hand for an entire month. Notice the difference between your hands. Which one feels better?

Spend a month not biting your fingernails. If you do, notice what you were thinking/doing when you did.

Look at your notes and figure out how you can address those specific thoughts/activities (I've noticed I bite my fingernails when I'm reading so I gave myself something to chew on while I read, like a toothpick).

The process sounds absurdly slow, but that's how it's supposed to work. Habit formation is tough and in some cases takes a very regulated approach to really set it. It's different for everyone, but if you've been struggling to form (or get rid of) a habit, it's an approach worth considering.